1. Field of the Invention
The present invention relates to an apparatus and method for producing an aperture for a lenslet array used, for example, in an autofocus camera.
2. Description of the Prior Art
In the Norman L. Stauffer U.S. Pat. No. 4,185,191, assigned to the assignee of the present invention, a range finding system for primary use in auto focus cameras is described utilizing a lenslet array with pairs of detectors behind each lenslet to receive radiation from a remote object and to produce, on the detector pairs, an image of the exit pupil of the camera taking lens. The detectors produce electrical signals for use by the system to determine the proper focus position for the remote object. In such a system, there is a need for a light blocking aperture between the lenslets to prevent radiation from reaching the detectors except by way of the lenslets. One aperture is shown in the Stauffer U.S. Pat. No. 4,425,501 where an opaque sheet or card with small holes therein is placed over the array so that the lenslets protrude through the holes. Another technique for forming the aperture is described in Japanese patent No. 55-106420 where the areas around the lenslets are painted or filled to block radiation. In my U.S. Pat. No. 4,695,719 assigned to the assignee of the present invention an aperture is created by solid state deposition techniques. All of these procedures require rather extensive labor to create the aperture and, in the case of the deposition technique, involve the making of a very accurate mask to expose a photoresist on the lenslet array to ultraviolet light. One solution to this latter problem has been proposed in the Rastko C. Maglic co-pending application Ser. No. 103,135 abandoned, Filed Sept. 28, 1987 and assigned to the assignee of the present invention.
In my co-pending application Ser. No. 020,634, filed Mar. 2, 1987 abandoned, and assigned to the assignee of the present invention, I disclosed a distributed aperture autofocus sensor which, utilizing a procedure described in the Robert H. Bellman U.S. Pat. No. 4,572,611, produces a lenslet array in which the individual lenslets are separated by columns of opaque partitions or barriers. These barriers extend between the lenslets throughout the material, usually glass, in which the lenslets are formed. As a result, cross over radiation from adjacent lenslets is reduced. Although in many cases, these barriers may take the place of an aperture, some radiation still penetrates the barriers making it desirable to have an aperture in addition to the barriers.
Any of the above described methods could be used to provide the desired aperture between the lenslets but each such method would continue to have the difficulties associated therewith.